EP0071250B1

EP0071250B1 - Swing-arm-type suspension with a lateral rod for an automotive vehicle

Info

Publication number: EP0071250B1
Application number: EP82106792A
Authority: EP
Inventors: Hideo Ito; Junsuke Kuroki; Namio Irie
Original assignee: Nissan Motor Co Ltd
Current assignee: Nissan Motor Co Ltd
Priority date: 1981-07-28
Filing date: 1982-07-27
Publication date: 1988-10-05
Also published as: DE3279084D1; US4537420A; EP0071250A2; EP0071250A3

Description

The present invention relates generally to a swing-arm-type automotive suspension as described in the preamble portion of claim 1, such as trailing-arm- or semi-trailing-arm-type suspension. More particularly, the invention relates to an automotive vehicle rear suspension of swing-arm type which has a laterally extending assist link which provides an improved suspension geometry with improved response of wheel alignment in response to outside forces.
In swing-arm-type automotive suspensions, wheel alignment is susceptible to positive camber and toe-out during compliance steering. These changes in wheel alignment will result in oversteer which degrades cornering stability and drivability of the vehicle. Such wheel alignment changes occur due to deformation of suspension geometry and/or bushings in the suspension structure. Changes in suspension geometry mainly influence roll steer and deformation of the bushing will affect compliance steering and camber change.
As is well known, in order to obtain better drivability and to optimize compensating cornering force in the suspension, it is necessary to restrict toe-out and positive camber during roll or compliance steering which would cause oversteer otherwise. For better drivability, the suspension should be slight understeering. To obtain understeering characteristics, compliance steering or roll steering must cause some toe-in (and) negative camber.
Restriction of compliance and roll steer and/or camber change can be achieved by providing sufficiently rigid bushings interposed between a suspension arm and a suspension member. However, by providing rigid bushings, pitching force such as winding-up moment and/or nose-dive moment applied to the vehicle during abrupt acceleration or deceleration of the vehicle cannot be satisfactorily absorbed. This will degrade the riding comfort of the vehicle.
Therefore, it is almost impossible to provide enough rolling force and satisfactory pitch absorbing effect with a swing arm type automotive rear suspension, in the prior art.
Cited GB-A-2 036 241 discloses a rear wheel suspension system for vehicles which restrains the rear wheel against deflection, resulting from lateral force, along the toe-in and toe-out directions, whereby the follow-up property of the rear wheel along the longitudinal direction of the vehicle is improved without sacrificing steering stability of the vehicle, thus resulting in improved vehicle riding.
However, cited GB-A-2 036 241 does not teach a toe-in change even when lateral forces are exerted on the vehicle body. This, in turn, means that said citation provides for linear or rather constant suspension geometry for providing linear steering characteristics. In the particular construction shown in the reference, since the lower arm is arranged substantially perpendicular to the axis of the radius rod at initial or neutral position, and since the bushing is arranged to absorb relative displacement between the lower arm and the radius rod, toe-in change may not occur during cornering.
According to the present invention, it is intended to provide a greater cornering force by causing toe-in change and/or negative camber change in response to vehicular rolling due to lateral force exerted on the vehicle body during cornering or curving. As is well-known, by causing toe-in and negative camber change in response to the lateral force, resistance against lateral slip of the vehicle becomes greater, which lateral slip tends to result in spin of the vehicle.
The afore-discussed object of the present invention is achieved by the subject-matter of new claim 1 and in particular by the features recited in the characterizing clause of new claim 1.
The present invention is to improve the rear suspension geometry in the swing-arm-type suspension in order to restrict compliance steering, roll steering and camber in response to outside force and maintain pitch absorbing effect at conventional level or improve the pitch absorbing effect. In order to achieve this, the swing arm suspension according to the present invention is provided with a lateral rod extending generally laterally toward the pivot axis of the suspension arm. The lateral rod serves mainly for lateral support and to restrict compliance or roll steering in the toe-out direction and to restrict positive camber change.
There is provided a swing arm suspension for automotive rear suspension, according to the present invention, which has a suspension arm pivotably attached to a suspension member for rotation about a substantially horizontal pivot axis. One end of a lateral rod is connected to the suspension arm via a bushing and the other end is connected to a suspension upper member via a bushing. The position where the lateral rod is connected to the suspension upper member is offset from an extension of the pivot axis of the suspension arm. The position is chosen such that the lateral rod augments the rolling compensation of the suspension to satisfactorily and successfully restrict roll or compliance steering in the toe-out direction and to restrict positive camber change. Preferably, the connecting end of the lateral rod should be connected to the suspension upper member at a position causing toe-in and/or negative camber.
According to the present invention, in conjunction the lateral rod, the suspension arm bushings interpositioned between the suspension arm and the suspension member are sufficiently flexible to satisfactorily absorb pitching force applied to the road wheel.

Brief Description of the Drawings

The present invention will be understood more fully from the detailed description given herebelow and from the accompanying drawings of the preferred embodiments of the present invention, which, however, should not be taken as limitative to the invention but for elucidation and explanation only.
In the drawings:

Fig. 1 is a perspective view of the first embodiment of a semi-trailing arm suspension according to the present invention;
Fig. 2 is an enlarged perspective view of the suspension arm in the first embodiment of the semi-trailing arm of Fig. 1;
Fig. 3 is a plan view of the semi-trailing arm suspension of Fig. 1;
Fig. 4 is a rear elevation view of the semi-trailing arm suspension of Fig. 1;
Fig. 5 is an explanatory illustration showing a suspension geometry on a horizontal plane and change thereof of the semi-trailing arm suspension of Fig. 1;
Fig. 6 is an explanatory illustration of a suspension geometry of the semi-trailing air suspension of Fig. 1 on a vertical plane, and showing movement of the suspension elements in response to a lateral force applied thereto;
Fig. 7 is an enlarged perspective view of a bracket applicable to the semi-trailing arm suspension of Fig. 1;
Fig. 8 is a bottom view of the bracket of Fig. 7;
Fig. 9 is a side elevation view of the bracket of Fig. 7;
Fig. 10 is a side elevation view of a bracket in the semi-trailing suspension of Fig. 1 for mounting the suspension arm to a suspension member;
Fig. 11 is a view similar to Fig. 10 but showing a modification of the bracket of Fig. 10;
Fig. 12 is a cross-section of the bracket of Fig. 11 shown engaged with the front end of the suspension arm;
Fig. 13 is a perspective view of a lateral rod applied the semi-trailing arm suspension of Fig. 1;
Fig. 14 is a longitudinal section view of the lateral rod of Fig. 13;
Fig. 15 is a perspective view of a modification of the semi-trailing arm suspension of Fig. 1;
Fig. 16 is a geometric illustration showing the operational features of another modification of the first embodiment of the semi-trailing arm suspension of Fig. 1;
Fig. 17 is a perspective view of the second embodiment of the semi-trailing arm suspension according to the present invention;
Fig. 18 is an enlarged cross section of a bushing assembly to be employed in the suspension of Fig. 18;
Fig. 19 is an enlarged cross-sectional view of the bushing assembly to be employed in the suspension of Fig. 18, which bushing assembly is a modification of that shown in Fig. 18;
Fig. 20 is a perspective view of the third embodiment of the semi-trailing arm suspension of the invention;
Fig. 21 is an enlarged perspective view of the lateral rod in the semi-trailing arm suspension of Fig. 20;
Fig. 22 is a sectional view taken along line A-A of Fig. 21;
Fig. 23 is a sectional view taken along line B-B of Fig. 21;
Fig. 24 is a perspective view of a modification of the lateral rod of Fig. 21;
Fig. 25 is a cross-sectional view of a bushing assembly of another modification of the lateral rod construction of Fig. 21;
Fig. 26 is a perspective view of the fourth embodiment of the semi-trailing arm suspension of the invention;
Fig. 27 is a cross-sectional view of a bracket in the suspension of Fig. 26 for mounting the suspension arm to the suspension member;
Fig. 28 is a rear elevation view of the bracket of Fig. 27.

Description of the Preferred Embodiments
Referring now to the drawings, particularly to Figs. 1 to 4, there is illustrated the preferred embodiment of a semi-trailing arm suspension for an automotive vehicle according to the present invention. As will be appreciated from Fig. 1, the semi-trailing arm suspension is employed in a front-wheel-drive vehicle. However, the invention is not intended to be limited to the semi-trailing-arm-type suspension but may include trailing arm or other swing arm suspensions, nor is the suspension in the present invention limited to a front-wheel-drive vehicle but is also applicable to a rear-wheel-drive vehicle.
The semi-trailing arm suspension generally comprises a suspension member 10 and a suspension arm 12 pivotably attached to the suspension member 10. The suspension member generally comprises part of a vehicle chassis and is connected at both ends to a vehicle body side frame (not shown). Bushings 14 are inserted between the suspension member 10 and the vehicle body side frame to isolate vibrations transmitted therebetween.
The suspension arm 12 comprises a suspension arm body 16 and a resilient member 18. The suspension arm body 16 has a wheel mounting portion 20 from which a spindle 72 extends laterally, a pivot portion 24 located at the front end thereof and provided with a hollow cylindrical end 26 which houses a bushing assembly 28. The pivot portion 24 doglegs inwardly from the wheel mounting portion 20 and the pivot portion 24 comprises an inner leg of the suspension arm body. The resilient member 18 is fixed to the outer vertical all of the suspension arm body with fastening bolts 30 and has an offset pivot portion 31 forward of the bolts 30. At the front end of the resilient member, there is provided a hollow cylindrical portion 32 for housing a bushing assembly 34. The longitudinal axis of the cylindrical portion 32 is aligned with that of the cylindrical end 26 of the suspension arm body 16. The pivot portions 24 and 31 are also inclined upwardly towards the front ends thereof.
The cylindrical end 26 and the cylindrical portion 32 are free to pivot about pivot bolts 36 and 38 respectively passing through the bushing assemblies 28 and 34 which engage inner and outer brackets 40 and 42 fixed to the rear vertical surface of the suspension member 10. Therefore, the axes of the pivot bolts 36 and 38 are in alignment to form a common pivot axis 37 of substantially vertical swing of the suspension arm 12 with respect to the suspension member 10.
On the other hand, the suspension arm 12 is suspended from the vehicle body (not shown) via a shock absorber assembly 44 including a shock absorber 46 and a suspension coil spring 48. The lower end of the shock absorber 46 is connected to the suspension arm 12 via a bracket 50 and the top thereof is connected to the vehicle body via a vibration-damping flange. The suspension coil spring 48 winds around the upper portion of the shock absorber between upper and lower spring seats 54. In this construction, the shock absorber assembly 44 is adapted to absorb most of the vertical road shock and resiliently suspend the suspension arm 12 from the vehicle body.
A lateral rod 56 has outer and inner ends 58 and 60 respectively provided with hollow cylindrical portions 62 and 64 for housing bushing assemblies 66 and 68. The outer end 58 with the bushing assembly 62 engages a pivot axle 70 extending from the rear end of the suspension arm 12 near the spindle 72 on which a wheel 74 and a wheel hub 76 are mounted. The inner end 60 of the lateral rod 56 is connected to an appropriate point of the vehicle body via a bracket 78. As shown in Figs. 3 and 4, the lateral rod 56 is inclined frontwardly and upwardly towards the bracket 78. The angle inclination of the lateral rod 56 is chosen to affect wheel alignment as described hereafter with reference to Figs. 5 and 6. The present invention is intended to adjust wheel alignment particularly in response to a lateral force applied thereto in the toe-in direction during compliance steer or roll steer, and in the negative camber direction. In order to achieve this, it is essential to offset the inner end of the lateral rod 56 from the pivot axis 37. Furthermore, it is necessary to elevate the inner end 60 of the lateral rod 56 relative to the outer end 58. Offsetting the inner end 60 of the lateral rod 56 from the pivot axis 37 is intended to provide different motion centers for the suspension arm 12 and the lateral rod to effectively cause mutual interference between independent movements of the suspension arm 12 and the lateral rod 56 to geometrically cause the desired wheel alignment changes. This will be described in detail hereinafter with reference to Figs. 5 and 6.
Figs. 5 and 6 are geometrical illustrations of the semi-trailing arm suspension of Figs. 1 to 4. In order to simplify the drawing of motions and reactions during compliance steering, roll steering and camber change, structural elements of the semi-trailing arm suspension of the present embodiment have been represented only by axes and points thereof. As shown in Fig. 5, the suspension arm 12 is suspended from the suspension member 10 via resilient bushings 28 and 34. The bushings 28 and 34 permit pivotal movement of the suspension arm 12 with respect to the suspension member 10. On the other hand, the lateral rod 56 is connected to the suspension arm 12 via the bushing 62 which permits the lateral rod to pivot relative to the suspension arm 123. In turn, the lateral rod 56 is connected to the vehicle body via the bushing 64. Here, in order to simplify the following explanation, the flexibility of the bushing 64 is ignored. In fact, the bushing 64 is flexible only in order to permit the lateral rod to move relative to the vehicle body in response to force applied to the wheel 74 which are, in turn, transmitted to the bushing 64 via the suspension arm 12 and the lateral rod 56. The deformation of the bushing 64 need not be considered in order to understand of the geometrical function of the shown embodiment.
Assuming a lateral force Fy is applied to the wheel 74, slight rotational motion occurs in the suspension arm 12 due to deformation of the bushings 28 and 34. As shown in Fig. 5, the motion center 80 of the suspension arm 12 is positioned between the bushings 28 and 34 along the pivot axis 37. Therefore, with the rotational axis 82 extending through the motion center 80, the suspension arm 12 responds to the angular moment to rotate slightly counterclockwise in Fig. 5. On the other hand, the lateral rod 56 rotates slightly about the bushing 64 in response to the lateral force applied through the suspension arm 12. By this, assuming the absence of the lateral rod 56, the point 84 from which the spindle 72 projects would move along a curve 86 according to the rotation of the suspension arm 12. On the other hand, assuming a stationary suspension arm 12, the bushing 66 would move along the curve 88 which would bring the lateral rod 56 closer to horizontal. The sum of the movements of the suspension arm 12 and the lateral rod 56 cause the point 84 to move along the curve 90. Due to the interference of the movements between the suspension arm 12 and the lateral rod 56, the total distance of the inward movement of the point 84 is reduced relative to either of the above assumed cases. As can be appreciated from Fig. 5, toe-out angle due to bushing compliance or roll steering is decreased.
On the other hand, as shown in Fig. 6, the point 84 is located at a level lower than that of the bushings 28 and 34 and the bushing 66 is even lower than the point 84. However, the vertical displacement between the point 84 and the bushing 66 is quite small and therefore can be ignored for consideration of the suspension geometry. The bushing 68 is positioned higher than the bushing 66 as set forth previously. Therefore, as can be understood, the length of the lateral rod in Fig. 5 is only the horizontal projection thereof and its real length is greater than the apparent length.
Centrifugal force is applied to the vehicle as it moves through a turn. This centrifugal force causes downward displacement of the outside of the vehicle body relative to the wheels. Therefore, the lateral rod 56 rotates upwardly about the bushing 64 to approach horizontal orientation. In this way, the point 84 is shifted outside in Fig. 5 to further reduce the toe-out angle or to cause toe-in during compliance steering or roll steering. The expansion of the lateral rod 56 along the horizontal causes negative camber rather than positive camber to increase cornering force. The camber angle is generally determined according to the inclination of the pivot axis which determines the rotational radius of the point 84 in the vertical direction. Therefore, as will be appreciated, camber angle will vary depending upon the inclination of the pivot axis with respect to the axis of the spindle and depending upon the orientation of the lateral rod 56. Thus, by carefully selecting the length of the lateral rod 56, camber can be chosen to be negative in order to increase cornering force.
To facilitate an appropriate wheel alignment, it would be easier to adjust the position of the bracket 78 suitably than to adjust the inclination of the suspension arm from the pivoted front end to the wheel mounting portion. Figs. 7 to 8 show detail of a bracket 78 which permits variation of the location thereof with respect to the outer end of the lateral rod 56. As shown in Figs. 7 and 8, the bracket 78 comprises a base section 781 to be mounted to the vehicle body and vertical sections 782 extending from both side edges of the base section 781. The vertical sections have through openings 783 to receive pivot bolts 784. On the other hand, the base section 781 is formed with a pair of elongated openings 785 through which fastening bolts 786 engage threaded openings (not shown) defined in the vehicle body. The elongated openings 785 are aligned parallel to the longitudinal axis of the lateral rod 56.
The bracket 78 is fitted to the vehicle body with the fastening bolts 786 passing through the elongated openings 785. The elongated openings 785 allow the bracket 78 to move back and forth with respect to the outer end of the lateral rod 56 to adjust the position of the bracket.
In the preferred embodiment, there is also provided adjusting means 560 for adjusting the length of the lateral rod 56. As shown in Figs. 13 and 14, the adjusting means 560 comprises an adjusting screw 561 formed with threaded portions 562 and 563 at both ends thereof. As will be appreciated, the threaded portions 562 and 563 are threaded in opposite directions. The lateral rod 56 is separated into outer and inner sections 564 and 565 which both have threaded bores 566 and 567 which engage the respective threaded portions of the adjusting screw 561. Thus, the length of the lateral rod 56 can be adjusted by rotating the adjusting screw 561 in either the expansion or the contraction direction via the grip portion 568.
On the other hand, adjustment of the inclination angle of the suspension arm towards the wheel mounting portion can be made by elongated curved openings 401 and 421 formed in the inner and outer brackets 40 and 42. As shown in Fig. 10, the longitudinal axes of the elongated curved openings 401 and 421 are directed substantially vertically to permit the displacement of the bushing assemblies 28 and 34 of the suspension arm 12 with respect to the mounting surfaces of the inner and outer brackets 40 and 42. The bushing assemblies 28 and 34 are secured to the inner and outer brackets 40 and 42 with the pivot bolts 36 and 38. The bushings 28 and 34 are movable up and down along the elongated curved openings 401 and 421 to adjust the inclination of the suspension arm 12 with respect to the horizontal plane passing through the pivot axis.
Figs. 11 and 12 show a modification of the inclination adjusting means of Fig. 10. In the shown embodiment, a specially constructed pivot bolt 402 is used to adjust the inclination of the suspension arm 12 with respect to the horizontal plane. As in the foregoing embodiment, the brackets 40 and 42 are formed with elongated curved openings 403 and 423. The pivot bolt 402 includes a head portion 404 offset from the axis of the threaded bolt section 405. A substantially triangular plate 406 connects the head portion 404 and the bolt section 405. The bolt section 405 is engageable with a fastening nut 407. On the other hand, the triangular plate 406 is provided a pin 408 projecting from the surface of the head portion 404 facing the brackets 40 and 42. The pin 408 is engaged with a recess 409 formed in the bracket 40 or 42 to constitute a pivot for movement of the triangular plate 406 with the bolt section 405 along the elongated curved openings 403 or 423. This way, as in the foregoing embodiment, the inclination of the suspension arm 12 with respect to the horizontal plane can be adjusted by turning the head portion 404.
As shown in Figs. 10 and 12, each of the bushing assemblies 28 and 34 comprises an outer metal cylinder 281, an inner metal cylinder 282 and an annular rubber bushing 283 interpositioned between the inner and outer metal cylinders 281 and 282. As is well known, the inner cylinder 282 extends from both ends of the outer cylinder 281 and the bushing 283 to define a clearance between the end of the bushing 283 and the wall of the bracket 40 or 42. The bushing 283 is formed with grooves 284 extending along the longitudinal axis thereof. The grooves 284 are diametrically opposed along the longitudinal axis of the legs of the suspension arm 12. These grooves 284 provide added flexibility for the bushing 283 with respect to pitching force applied thereto. Since the pitching force is generally applied along the longitudinal axis, the grooves 284 satisfactorily absorbs the pitching moment applied to the vehicle body from the wheel 74. As set forth previously, the rolling force or cornering force is maintained at least at the conventional level or increased in cooperation with the lateral rod.
Fig. 15 shows a modification of the suspension arm in the semi-trailing arm suspension of Figs. 1 to 4. In the shown modification, the arm body 16 comprises an outer leg 102 with a cylindrical end 104. A resilient member 106 is in the form of an inner leg 108 with the cylindrical portion 110 is attached to the inner vertical surface of the arm body 16. The cylindrical portion 110 of the resilient member 106 houses the bushing assembly 112.
As in to the foregoing first embodiment of Figs. 1 to 4, the lateral rod 56 extends laterally from the rear end of the suspension arm 12. The lateral rod 56 is also connected to the vehicle body through the bracket 78.
In the two foregoing embodiments, the resilient members 18 and 106 cause the suspension arm to be deformed in the direction of toe-in during compliance steering and roll steering and cause negative camber simultaneously. In this way, in response to lateral forces applied to the wheels, the resilient members 18 and 106 are deformed to cause toe-in and negative camber to increase cornering force.
Fig. 16 shows another modification of the first embodimeiit, in which wheel alignment is modified to more satisfactorily cause toe-in and negative camber. In this embodiment, the lateral rod 120 is inclined such that the inner end 122 is rearward of the outer end 123 thereof. As shown in Fig. 16, the pivot axis 37 is inclined at an angle y with respect to the lateral axis normal to the longitudinal axis of the vehicle body. On the other hand, the lateral rod 120 is provided a rearward inclination of an angle P.
In this construction, assuming the absence of the lateral rod 120, the suspension arm 12 moves about a motion center 80 with motion axis 82 in response to lateral forces applied to the wheel 74. The path of displacement of the point 84 is as represented by line 124. The lateral rod 120 interferes with the movement of the point 84 along the curve 124. Ignoring the displacement of the suspension arm, the outer end 123 of the lateral rod 120 would move along the curve 125. At this time, since the pivotal point of the lateral rod 120, i.e., the inner end 122, is rearward of the outer end 123, the radius line 125 extends outwardly of the point 84. Thus, the point 84 moves in response to the lateral force along a curve represented in phantom lines 126 shifted outwards of the curve 124. As a result, movement of the point 84 resulting in toe-out during compliance steering and roll steering is reduced. The interference between the movements of the suspension arm 12 and the lateral rod 120 cause toe-in to provide slight understeering characteristics in this suspension geometry.
Referring to Figs. 17 and 18, the second embodiment of a semi-trailing arm suspension for an automotive vehicle according to the present invention is illustrated.
As in the foregoing first embodiment, the semi-trailing arm suspension generally comprises a suspension member (not shown) and a suspension arm 212 pivotably connected to the suspension member. The suspension arm 212 comprises a suspension arm body 216 and a pair of leg portions 217 and 218. The suspension arm body 216 has a wheel mounting portion 220 from which a spindle 272 extends laterally. The leg portions extend frontwards from the arm body 216 and are provided with inner and outer cylindrical ends 226 and 227 which house bushing assemblies 228 and 229 respectively. The pivot axis 224 passing through the cylindrical ends, 226 and 227, is inclined with respect to the lateral direction of the vehicle body.
The cylindrical ends 226 and 227 pivot about pivot bolts 236 and 238 respectively passing through the bushing assemblies 228 and 229 and fixed to inner and outer brackets 240 and 242 fixed to the rear vertical surface of the suspension member adjacent both ends thereof. Therefore, the axes of the pivot bolts 236 and 238 are in alignment to form a common pivot axis 224 for substantially vertical swing movement of the suspension arm 212 with respect to the suspension member.
On the other hand, the suspension arm 212 is suspended from a vehicle body (not shown) via a shock absorber assembly 244 including a shock absorber 246 and a suspension coil spring 248. The lower end of the shock absorber 246 is connected to the suspension arm 212 via a bracket 250. The top end of shock absorber 246 is connected to the vehicle body via a vibration damper 252. The suspension coil spring 248 winds around the upper portion of the shock absorber between upper and lower spring seats 254. In this construction, the shock absorber assembly 244 is adapted to absorb most of the vertical shock and to resiliently suspend the suspension arm 212 from the vehicle body.
A lateral rod 256 has outer and inner ends 258 and 260 respectively provided with cylindrical portions 262 and 264 to house bushing assemblies 266 and 268. The outer end 258 with the bushing assembly 262 is engaged with an axle 270 extending from the rear end of the suspension arm 212 near the spindle 272, which rotatably supports a wheel 274 and a wheel hub. The inner end 260 of the lateral rod 256 is connected to the vehicle body via a bracket 278. The lateral rod 256 is inclined frontwardly and upwardly towards the bracket 78. The inclination angle of the lateral rod 56 is chosen so as to cause the wheel alignment, particularly in response to lateral forces, to reduce toe-out or to cause toe-in.
As shown in Fig. 18, the bushing assemblies 228 and 229 respectively comprise an outer cylinder 290, an inner cylinder 292 and a rubber bushing 293. The outer cylinder 290 has a radially extending flange 294 at one end. The rubber bushing 293 extends axially from both ends of the outer cylinder 290 along the entire length of the inner cylinder 292 and has radially extending flange portions 295 and 296. The diameter of the flange portion 295 is larger than that of the flange portion 296. The axial length of the outer cylinder 290 corresponds to that of the cylindrical end 226 or 227 of the leg portions 217 or 218 of the suspension arm 12. The radially extending flange 294 of the outer cylinder 290 is adapted to contact the axial edge of the cylindrical end 226 or 227.
The bushing assemblies 228 and 229 are respectively arranged to position the flange portions 295 outwards of the other flange portions 296. In this way, the rigidity at the outer end of the bushing assemblies 228 and 229 exceeds that at the inner ends. This gives to the suspension arm a tendency to move in the direction of toe-in during compliance steering or roll steering in response to the lateral forces.
Fig. 19 shows a modification of the bushing assembly of Fig. 18. In this modification, the bushing assembly comprises the outer cylinder 290', the inner cylinder 291' and outer and inner bushings 292' and 293'. The rubber bushings 292' and 293' are made of materials with different bulk elastic moduli. The rigidity of the outer bushing 292' is higher than that of the inner bushing 293'. This way, same effect on compliance steering or roll steering characteristics can be obtained.
Figs. 20 to 23 show the third embodiment of the semi-trailing arm suspension of the present invention. In this embodiment, deformation of the bushings can be limited or restricted in order to extend the life of the bushings. As shown in Fig. 20, the semi-trailing arm suspension in this embodiment has a structure similar to that set forth with respect to Fig. 1.
As shown in Fig. 20, the semi-trailing arm suspension generally comprises a suspension member and a suspension arm 312 hinged to the suspension member. The suspension arm 312 comprises a suspension arm body 316 and a resilient member 318. The suspension arm body 316 has a wheel mounting portion 320 from which a spindle 372 extends laterally and a pivot portion 324 located at the front end thereof provided with a cylindrical end 326 for housing a bushing assembly 328. The pivot portion 324 is inwardly from the wheel mounting portion 320 and forms an inner leg of the suspension arm. A resilient member 318 is fixed to the outer vertical wall of the suspension arm body and has a pivot portion 331 near the front end thereof. At the front end of the resilient member, there is provided a cylindrical portion 332 for housing a bushing assembly 334. The cylindrical portion 332 is in aligned with the longitudinal axis of the cylindrical end 326 of the suspension arm body 316. The pivot portions 324 and 331 slope upwards towards the pivotal axis thereof.
The cylindrical end 326 and the cylindrical portion 332 pivot about pivot bolts passing through the bushing assemblies 328 and 334 and engaging the inner and outer brackets fixed to the rear vertical surface of the suspension member. Therefore, the axes of the pivot bolts are aligned to form a common pivot axis 337 for substantially vertical swing movement of the suspension arm 312 with respect to the suspension member.
On the other hand, the suspension arm 312 is suspended from the vehicle body (not shown) via a shock absorber assembly 344 including a shock absorber 346 and a suspension coil spring 348. The lower end of the shock absorber 346 is connected to the suspension arm 312 via a bracket 350 and the top thereof is connected to the vehicle body via a vibration damper 352. The suspension coil spring 348 winds around the upper portion of the shock absorber between upper and lower spring seats 354. In this construction, the shock absorber assembly 344 is adapted to absorb most of the vertical shock and to resiliently suspend the suspension arm 312 from the vehicle body.
A lateral rod 356 has outer and inner ends 358 and 360 respectively provided with cylindrical portions 362 and 364 which house bushing assemblies 366 and 368. The outer end 358 with the bushing assembly 362 engages an axle 370 extending from the rear end of the suspension arm 312 near the spindle 372, which rotatably supports a wheel 374 and a wheel hub 376. The inner end 360 of the lateral rod 356 is connected to the vehicle body via a bracket 378. As shown in Figs. 21 to 23, the lateral rod 356 is inclined frontwardly and upwardly towards the bracket 378.
With the construction as set forth, the bushing assemblies 366 and 368 are respectively constructed as shown in Figs. 22 and 23. Each of the bushing assemblies 366 and 368 comprises an outer cylinder 380, an inner cylinder 381 and an annular rubber bushing 382. The rubber bushing 382 is formed with arcuate grooves 383 and 384 which are diametrically opposed along the longitudinal axis of the lateral rod 356. As apparent from Fig. 23, the grooves 383 and 384 extend only part of the way through the axial interior 385 of the bushing 382.
In this bushing assembly construction, the bushing assemblies 366 and 368 exhibit differential rigidity radially. Specifically, the bushing assemblies 366 and 368 are easily deformed along the longitudinal axis of the lateral rod 356 until the grooves 383 and 384 are completely closed. Therefore, the lateral rod 356 will not interfere so significantly when the suspension arm 312 moves up and down in response to vertical road shocks on the wheels. This reduces stress on the bushing assemblies 366 and 368 caused by distortion of wheel alignment in response to lateral forces in order to expand the lifetime of the rubber bushings 382.
Therefore, even if the rigidity of the rubber bushing 382 is relatively high, this will not influence absorption of road shock. In other words, rather rigid bushings can be used in the bushing assemblies 366 and 368 to increase driving stability.
The same effect can be achieved with various bushing assembly structures. For example, the radial position of the grooves can be shifted to the axis normal to the longitudinal axis of the lateral rod 356. In addition, as shown in Figs. 24 and 25, the equivalent effect can be achieved by adjusting the shape of the bushing assembly. In the example of Fig. 24, the bushing assembly 390 has a truncated hourglass configuration. On the other hand, in the example of Fig. 25, the bushing assembly 392 is formed with an oval cross-section. The elongated axis of the oval cross-section of the bushing 392 is aligned vertically. With these structures, the bushing assemblies will not influence absorption of vertical shocks. In turn, the lateral rod 356 satisfactorily and effectively restricts the movement of the suspension arm 312 about its motion center to cause toe-in or to reduce toe-out.
Figs. 26 to 28 show the fourth embodiment of the semi-trailing arm suspension. As in the foregoing embodiments, the suspension arm 412 is hinged to the suspension member (not shown) via the inner and outer brackets 440 and 442. The shock absorber assembly 444 is interpositioned between the suspension arm 412 and the vehicle body (not shown) to resiliently suspend the suspension arm from the vehicle body. The lateral rod 456 is inserted between the vehicle body and the suspension arm 412 substantially laterally with respect to the plane of motion of the suspension arm. The construction of the present semi-trailing suspension is similar to the foregoing embodiment of Fig. 17.
In the shown embodiment, the bracket 442 includes another absorber bushing therein. As shown in Figs. 27 and 28, the bracket 442 comprises an outer bracket 460 and an inner bracket 461. The outer bracket 460 is fixedly secured to the vehicle body 463 with fastening bolts 464 and nuts 465. To the lower surface of the outer bracket 460, a crank-shaped member 466 is secured. Between the lower surface of the outer bracket 460 and the upper surface of the crank shaped member 466, rubber plates 467 and 468 are inserted. The rubber plates 467 and 468 sandwich a section 469 of the inner bracket 461 therebetween to resiliently suspend the inner bracket 461 from the outer bracket 460. The inner end 470 of the lateral rod 456 is engaged to the inner bracket 451 via the pivot bolt 471.
In the preferred construction, the rubber plates 467 and 468 are provided with differential rigidity so that the rigidity in the pitch direction of the vehicle is lower than that in other directions. This way, pitch moment damping can be effectively done in cooperation with the bushings 428 and 434 of the suspension arm.
Therefore, as described hereabove, the present invention can fulfil all of the objects and advantages sought thereto.
It should be noted, however, the present invention should not be limited to the foregoing embodiments specifically illustrated. For example, the inclination of the lateral rod can be varied any way as long as it serves to restrict toe-out during compliance steering or roll steering. Also, the specific constructions in each part of the foregoing embodiments can be modified and/or embodied otherwise without departing from the principle of the invention. Furthermore, however all the embodiment shown hereabove have been directed to semi-trailing-arm-type suspension, this can also be applied for any swing arm suspension, particularly for a full-trailing arm type suspension.

Claims

1. A swing arm suspension for an automotive vehicle of the type comprising: a vehicle body; a suspension arm (12, 212, 312, 412) having a rear portion (20, 220) rotatably supporting a wheel (74, 274) and having a front portion (24, 224) pivotably connected to said vehicle body for vertically pivoting movement with respect to a pivot axis (37, 337) between said vehicle body and said suspension arm, said pivot axis crossing a longitudinal axis of the vehicle; further comprising a lateral rod member (56, 256, 356, 456) having an outer end (58, 258, 358) connected to said rear portion of said suspension arm and having its inner end (60, 260) connected to said vehicle body, said lateral rod member inner end being connected to said vehicle body at a point offset from said pivot axis (37, 337), characterized in that the lateral rod member inner end (60, 260, 460) is connected to the vehicle body at a point above the level of the lateral rod member outer end (58, 258, 358) so that said lateral rod moves the wheel on the suspension arm to a negative camber position in response to cornering force, and in that said suspension arm (12, 212, 312, 412) is suspended from said vehicle body via two spaced apart flexible bushings (28, 34; 228, 238, 324, 334; 428, 434) which are arranged along said pivot axis such that a motion centre (80) of the suspension arm is positioned between said two flexible bushings.

2. A swing arm suspension according to claim 1, characterized in that the suspension (12, 212, 312,412) comprises a spindle (72) at a first section thereof for rotatably supporting the wheel (74, 274) and a pair of pivot portions pivotably connected to said vehicle body along a common pivot axis to permit substantially vertical swing movement of said suspension arm (12, 212, 312, 412) about the common pivot axis thereof; and in that the rod member (56, 256, 356, 456) is connected to a second section of said suspension arm at a first end thereof and to a vehicle body at a second end thereof and extends therefrom such that said first end and said second end thereof and said pair of pivot portions of said suspension arm define a quadrilateral.

3. The suspension as set forth in claims 1 or 2, characterized in that said second end of said rod member (56, 256, 356, 456) is connected to said vehicle body via a bracket having means (560) for adjusting the location of said second end of said rod member with respect to said first end thereof.

4. The suspension as set forth. in claim 3, characterized in that said adjusting means (560) has elongated openings formed in said bracket for permitting the latter to move along the longitudinal axis of said rod member.

5. The suspension as set forth in claim 4, characterized in that said adjusting means (560) also has an adjusting screw (561) integral to the rod member which is separated into outer and inner sections, said adjusting screw (561) adjusting the distance between the opposing ends of said outer and inner sections to thereby adjust the overall length of said rod member.

6. The suspension as set forth in claim 3, characterized in that said pivot portions of said suspension arm are connected to said vehicle body via a bracket having means for adjusting the inclination of said suspension arm with respect to the horizontal plane.

7. The suspension as set forth in claim 6, characterized in that said inclination adjusting means has a pair of elongated curved openings (401, 421) formed in said bracket (40, 42), which elongated curved openings are engageable with pivot axle for pivoting said front end of said suspension arm relative to said vehicle body and guide the vertical adjusting movement of said pivot axle therealong.

8. The suspension as set forth in claim 3, characterized in that said pivot portions of the suspension arm (12, 212, 312, 412) are connected to said vehicle body via a bushing assembly which includes means for providing an isotropic rigidity in order to provide sufficient flexibility in relation to vertical forces applied to the vehicle and sufficient rigidity for lateral forces.

9. The suspension as set forth in claim 8, characterized in that said an isotropic rigidity providing means has grooves (284) formed in said bushing assembly diametrically opposing one another along the longitudinal axis of the suspension arm.

10. The suspension as set forth in claim 8, characterized in that said bushing assembly has different rigidity at the outer and inner sections thereof such that it has a tendency to cause change in the wheel alignment in the toe-in direction.